Spatial diversity is an effective diversity technique used in multiple antenna wireless systems.
It requires that antenna elements be sufficiently distributed by at least ten times the signal
wavelength (10λ). Sufficient spatial distribution of antenna elements renders performance
improvements through diversity gain. In consumer electronics, antenna elements are often
located in close proximity, < λ, due to form size constraints. Therefore performance improvement through spatial diversity is limited even though multiple antenna systems are employed.
The work in this dissertation addresses the use of power line communication as a method to
spatially distribute antenna elements of a multiple antenna wireless system. Addressing this
problem requires the cooperative use of both wireless and powerline channels to form a hybrid
channel.
A hybrid powerline-wireless channel is defined as the concatenation of a powerline channel and
a wireless channel to establish a unified channel. A sequence-based channel sounding approach
using maximum length sequences and software-defined radio was designed, implemented andapplied to attain channel transfer characteristics of the hybrid channel. The measurement
campaign was carried out for an indoor low-voltage level powerline network. The attained
results include the channel impulse responses, frequency responses and power delay profiles.
Coherence bandwidth, average channel attenuation and power delay profile timing delays
are channel parameters that were extracted from the measurements. The extracted channel
parameters reveal that the hybrid channel is a challenging medium for data transfer and
communication applications.
Based on the attained hybrid channel characterisation parameters, a physical layer structure
for a 1 × 2 single-input multiple-output orthogonal frequency division multiplexing (SIMOOFDM) hybrid powerline-wireless system was designed and implemented. An investigation of
the bit-error-rate performance of single-carrier and multi-carrier modulation for a multipath
powerline channel was carried out in simulation. Using OFDM as a suitable candidate for
multi-carrier modulation, it was found to outperform single-carrier modulation. OFDM was
used as the channel access method for the hybrid channel. Source encoding and decoding of
the physical layer structure was designed to be robust against inherent interferences of the
hybrid channel. Selection combining, equal gain combining and maximal ratio combining
methods were designed and implemented. Estimation methods for error rate, data transfer
rate and SNR of the SIMO-OFDM system were designed and implemented. Capacitive signal
coupling was used to interface the powerline channel to the wireless propagation environment,
hence establishing the hybrid channel. This method also allowed powerline transmission to be
performed at a much lower frequency than wireless transmission.
An experiment was conducted to investigate the effect of spatial distribution on the 1 × 2
SIMO-OFDM hybrid powerline-wireless system for indoor environments. The results of the
experiment were error rate curves produced for different spatial distribution lengths through a
powerline channel for each signal combining method. Error rate performance improvements in
the SIMO-OFDM system were achieved with an increase of antenna element spatial distribution
due to lowered signal envelope correlation. Small but yet notable diversity gains were observed
by the increase in the slope of the produced error rate and signal-to-noise ratio curves for each
signal combining method. Experimental parameters and apparatus placed a limitation on
the achievable spatial distribution of diversity branches, hence the achievable diversity gains.
This was a result of overwhelming inherent interferences of the hybrid channel / Dissertation (MEng)--University of Pretoria, 2020. / CeTEIS / Electrical, Electronic and Computer Engineering / MEng / Unrestricted
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:up/oai:repository.up.ac.za:2263/75857 |
| Date | January 2020 |
| Creators | Mokise, Kealeboga |
| Contributors | Myburgh, Hermanus Carel, u13241142@tuks.co.za |
| Publisher | University of Pretoria |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | © 2019 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
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